Tools and Methods for Forming Semi-Transparent Patterning Masks

ABSTRACT

Means, apparatus, systems, and/or methods are described for forming improved rigid or flexible semi-transparent imprinting templates. These templates can be used to produce patterning masks having improved resolution that do not require plasma etching for residue removal. The methods and apparatus are compatible with roll-to-roll manufacturing processes and enable roll-to-roll formation of a wide range of metal patterned films.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.13/302,731, filed 22 Nov. 2011 and entitled “Tools and Methods forForming Semi-Transparent Patterning Masks” which claims priority to U.S.Provisional Patent Application No. 61/416,011, filed 22 Nov. 2010, andentitled “Tools and Methods for Forming Patterning Masks,” the entirecontent of both of which is incorporated by reference herein. Thisapplication is related to the following applications, each of which isincorporated herein by reference in its entirety: U.S. application Ser.No. 11/337,013 filed 20 Jan. 2006 and entitled “Replication Tools AndRelated Fabrication Methods and Apparatus”; U.S. application Ser. No.11/471,223 filed 26 Jun. 2006 and entitled “Systems and Methods forRoll-to-Roll Patterning”; U.S. application Ser. No. 11/711,928 filed 27Feb. 2007 and entitled “Formation of Pattern Replicating Tools”; U.S.application Ser. No. 11/830,718 filed 30 Jul. 2007 and entitled“Addressable Flexible Patterns”; and, U.S. application Ser. No.12/270,650 filed 13 Nov. 2008 and entitled “Methods and Systems forForming Flexible Multilayer Structures”.

BACKGROUND

Microscale and nanoscale patterns are used in a wide range of photonicand electronic devices and applications, including organic lightemitting diodes (OLEDs), photovoltaic cells, thin-film electroniccircuits, information displays, touch screens, wire-grid polarizers,metamaterial films, sensors, and many others. These devices may includecomponents and sub-assemblies having very fine-scale circuitry andelectrically conductive elements, typically fabricated using highresolution graphic arts techniques and/or semiconductor lithography.

High-resolution printing, including gravure, ink jet, etc., is arelatively inexpensive process and, limited by print resolution, is usedto make the coarser patterns of these devices, typically ranging fromhundreds of microns down to roughly ten microns in width. The electricalconductivity of traces made by “printed electronic” techniques,typically using metal particle or metal precursor type inks, aregenerally inferior to those made from bulk metals and often requirethermal post-processing to achieve acceptable electrical conductivity.For producing patterns in the micron to submicron and nanometer regime,a newer process, nanoimprint lithography (NIL), is being used as analternative to optical lithography, which is very expensive fornanometer-scale features. In NIL, a 3-dimensional (3D) master pattern(template or mold) is placed into contact with a layer of a liquid ordeformable solid polymeric material, followed by the application of someamount of pressure, resulting in the polymeric material flowing into thetemplate cavities to form the complementary structure. If the polymermaterial is in the form of a solid layer, heat or chemical treatment isused to soften the layer and allow it to flow into the template. Afterthe material is solidified (either by reducing the temperature below thematerial's Tg or by radiation crosslinking), the template and polymerlayer are separated, whereupon the polymer layer will have the(complementary) surface structure of the template.

NIL can also used to form a polymeric etch mask, essentially a stencilthrough whose openings material can be deposited or removed. Insemiconductor lithography, such mask structures are commonly formed in aspin-coated photoresist material using optical exposure through aphotomask, by direct laser or e-beam writing, or by the newer NILprocess. On significant advantage of the NIL approach over opticallithography, particularly in forming very small (<100 nm) features, isthat the expensive and complex optical exposure process is replaced by amuch simpler mechanical imprinting process. In addition, as a parallelprocess, it is significantly faster than serial process of direct writelithography.

One limitation, however, of the NIL process for forming etch masks isthat a very thin layer of residual polymeric material (known as the‘residue’ or ‘scum’ layer) is left in the bottoms of the mask (i.e.,closest to the substrate on which the mask is formed) after imprinting,and this layer must be removed prior to further processing (depositionor removal). Incomplete removal of the residual material from the maskwill result in defects after subsequent steps: e.g., patches of missingmetal after metallization in additive processing and stray patches ofmetal after etching in subtractive processing.

Residue removal (also known as ‘de-scumming’) is usually carried out byplasma (or reactive ion) etching, a vacuum process that is used toselectively remove unwanted organic or other material. Although ideallythis is an anisotropic process, where material perpendicular to thesource direction is removed at a faster rate than that in the paralleldirection, this is not always the case, resulting in potentiallysignificant unwanted etching of critical mask features, for example thatresults in widened mask openings that produces incorrect line widths.

In addition, the residue removal process has other drawbacks: 1) itrequires expensive vacuum equipment with specialized gas handling andcontrols, 2) pump-down time to reach operation pressure adds to theprocessing time, 3) the etch process itself can be slow, also adding tothe process time, 4) non-uniformities in the plasma field can causenon-uniform polymer removal and result in areas that are under-etched(areas of residue left intact) or over-etched (areas of mask polymerremoved), and/or 5) the etch process can be detrimental to otherelements of the structure (including by unwanted material removal,chemical interactions, re-deposition of etch by-products, hardening ofthe mask, etc.).

It is thus very desirable to be able to form mask layers that do notrequire plasma etch removal of the residue layer. Several processes havebeen developed and art well known to the art for doing this, includingthe use of semi-transparent or hybrid imprint masks and by modificationof the surface-mask polymer wetting properties. Cheng and Gou (XingCheng and L Jay Guo, One-Step Lithography For Various Size Patterns Witha Hybrid Mask-Mold, Journal Microelectronic Engineering, Vol. 71, No.3-4, pg. 288-293, May 2004), Liao and Hsu (Wen-Chang Liao and SteveLien-Chung Hsu, High Aspect Ratio Pattern Transfer in ImprintLithography Using a Hybrid Mold, J. Vac. Sci. Technol. B 22, 2764, 2004)and Schift, et al. (Helmut Schift, Christian Spreu, Arne Schleunitz,Jens Gobrecht, Anna Klukowska, Freimut Reuther, and Gabi Gruetzner, EasyMask-Mold Fabrication for Combined Nanoimprint and Photolithography, J.Vac. Sci. Technol. B 27, 2850, 2009) describe “hybrid mask-mold”processes (also known as Combined Nanoimprint and Photolithography, orCNP) in which certain portions of an imprint mask include thin filmmetal areas that block incident light and thereby prevent crosslinkingof the underlying polymer material (what would otherwise be theresidue), which is thus developable during subsequent processing. Inanother variant of this approach, Kao et al (Po-Ching Kao, Sheng-YuanChu, Chuan-Yi Zhan, Lien-Chung Hsu, Wen-Chang Liao, Fabrication of thePatterned Flexible OLEDs Using a Combined Roller Imprinting andPhotolithography Method, 5th IEEE Conference on Nanotechnology, Volume2, 693-695, 2005) used a hybrid mask in Hua et al. (Hua Tan, AndrewGilbertson, and Stephen Y. Chou, Roller Nanoimprint Lithography, J. Vac.Sci. Technol. B 16, 3926, 1998) for a roller press nanoimprintlithography process. In non-CNP approach to “nonresidual layerimprinting”, Pina-Hernandez et al (Carlos Pina-Hernandez, Jin-Sung Kim,Peng-Fei Fu, and L. Jay Guo, Nonresidual Layer Imprinting and NewReplication Capabilities Demonstrated for Fast Thermal CurablePolydimethysiloxanes, J. Vac. Sci. Technol. B 25 (6), November/December2007) described a process in which thermal curable polydimethylsiloxaneresists and fluorinated silane surface treatments were found in certaininstances to form structures without residual layers.

However, each of these approaches has certain limitations and drawbackswhich the subject technology, as will be described below, overcomes. Insome approaches, such as with “nonresidue layer imprinting”, therequirement of a particular surfaces and surface treatments to reduce oreliminate the residue layer works under a restricted set of conditions,and further is not compatible with a broad range of materials,geometries or processes. In the case of the hybrid mask-molds, very thinmetal films are used for the absorbing layers, which can result in lightleakage into adjacent structures and partial exposure of the residueareas (Schift et al, FIG. 5). Furthermore, all of these processes userigid substrates (glass, quartz) substrates which can be etched toproduce the hybrid mask. Such masks are relatively fragile and expensiveand are inflexible so as not to be suitable for commercial high-volumemanufacturing, and in particular for roll-to-roll manufacturing.

SUMMARY

The subject technology addresses the previously-noted limitations, andcan provide improved methods for forming semi-transparent (‘S-T’)imprint tools (templates or molds) for use in producing residue-freepatterning masks and application of such method to produce large-areasemi-transparent films. The improvements inherent to the subjecttechnology, as described in detail below, can include higher resolutionpatterning, rapid and low-cost tool fabrication, the ability to formtools that are rigid or flexible, alteration of the aspect ratio of therelief features, and elimination of the need for costly (and relativelyslow) plasma etching step for mask residue removal. The subjecttechnology, therefore, can offer a significant improvement over theprior art used to form and use imprint tools. In a further embodiment,the process for forming semi-transparent tools of the subject technologycan be carried out in a continuous roll-to-roll manner in order toeither create large quantities of such tools, or to form transparentpatterned electrically conductive films.

The subject technology, therefore, is of particular value when appliedto high-volume roll-to-roll production of materials and devices in whichlithographic relief masks are used for subtractive and/or additiveprocessing due to the elimination of the roll vacuum plasma etchingstep. This step represents a significant manufacturing process“bottleneck” with high capital costs, relatively low throughput, andincreased production times. By completely eliminating this bottleneck,production throughput is greatly increased and costs associated withpatterning are greatly reduced. The methods of the subject technologycan therefore be applied, for example, to the low-cost roll-to-rollproduction of high-resolution patterned conductors.

The above summary of the subject technology is not intended to describeeach embodiment of every implementation of the subject technology. Itwill be understood by one skilled in the art that the embodimentsdepicted in the drawings are illustrative and variations of those shownas well as other embodiments described herein may be envisioned andpracticed within the scope of the disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.They do not set forth all embodiments. Other embodiments may be used inaddition or instead. Details that may be apparent or unnecessary may beomitted to save space or for more effective illustration. Conversely,some embodiments may be practiced without all of the details that aredisclosed. When the same numeral appears in different drawings, itrefers to the same or like components or steps. The drawings are notnecessarily to scale, emphasis instead being placed on the principles ofthe disclosure. In the drawings:

FIG. 1 shows a cross-sectional view of an example of a transparentsubstrate coated with a seed layer and a relief pattern mask on the seedlayer, with the seed layer selectively exposed through the openings inthe pattern mask, in accordance with the subject technology.

FIG. 2 is a cross-sectional view of the structure of FIG. 1 in whichmetal has been deposited in and partially filled the mask openings.

FIG. 3 is a cross-sectional view of the structure of FIG. 2 in which themetal has completely filled the mask openings.

FIG. 4 is a cross-sectional view of the structure of FIG. 2 in which atransparent upper substrate is attached to the lower structure with atransparent adhesive layer.

FIG. 5 is a cross-sectional view of the structure of FIG. 3 in which atransparent upper substrate is attached to the lower structure with atransparent adhesive layer.

FIG. 6 a is a cross-sectional view of the structure of FIG. 5 with thelower substrate separated from the upper structure.

FIG. 6 b is a cross-sectional view of the structure of FIG. 5 with thelower substrate and seed layer separated from the upper structure.

FIG. 6 c is a cross-sectional view of the structure of FIG. 5 in whichthe metal layer is separated from the lower substrate, seed layer andimprinted layer.

FIG. 7 a is a cross-sectional view of the structure of FIG. 6 b in whichthe metal layer has been deposited to fill the mask layer.

FIG. 7 b is a cross-sectional view of the structure of FIG. 7 a in whichthe mask polymer has been partially removed.

FIG. 7 b is a cross-sectional view of the structure of FIG. 7 a in whichthe mask polymer has been partially removed.

FIG. 7 c is a cross-sectional view of the structure of FIG. 7 a in whichthe mask polymer has been fully removed.

FIG. 7 d is a cross-sectional view of the structure of FIG. 7 a in whichthe mask polymer has been fully removed and the adhesive layer partiallyremoved.

FIG. 7 c is a cross-sectional view of the structure of FIG. 7 a in whichthe mask polymer has been fully removed.

FIG. 7 e is a cross-sectional view of the structure of FIG. 7 d in whichthe metal layer has been overcoated with a conformal release layer.

FIG. 8 a shows structure of FIG. 7 c in contact with a metallized lowersubstrate and an imprint material in the presence of radiation used toharden the imprint material.

FIG. 8 b shows structure of FIG. 8 a after exposure of the imprintmaterial through the upper structure (semi-transparent imprinting tool),showing hardened and non-hardened imprint material.

FIG. 8 c shows structure of FIG. 8 b after separation of thesemi-transparent imprinting tool.

FIG. 8 d shows structure of FIG. 8 c after removal of the non-hardenedimprint material.

FIG. 9 is a cross-sectional view of an example of apparatus forproducing continuous films of semitransparent material for imprint toolsor for transparent conductive films.

FIG. 10 is a cross-sectional view of an example of continuousroll-to-roll apparatus for producing polymer masked films that do notrequire plasma etch residue removal.

While certain embodiments are depicted in the drawings, one skilled inthe art will appreciate that the embodiments depicted are illustrativeand that variations of those shown, as well as other embodimentsdescribed herein, may be envisioned and practiced within the scope ofthe present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, and/ortechniques have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The subject technology is directed toward improved methods and systemsfor forming rigid and flexible semi-transparent (S-T) imprint tools. Asignificant advantage of such tools is that they can be used to makeimprint lithography masks that do not require plasma etching to removethe residue (scum) material that is an unwanted characteristic of theformation of such masks. Such plasma-etch-free masks, when used with themethods of additive and/or subtractive pattern formation processes knownto the art, are useful in the formation of many types of patternedmaterials and devices, such as described above. The subject technologycan provide a continuous roll-to-roll process utilizing semi-transparentimprint tools to form plasma-etch-free masks. Further, the subjecttechnology can provide a continuous roll-to-roll process for producingsuch plasma-etch-free masks semi-transparent films for use astransparent electrical conductors.

A significant distinction exists between the widely-used conventionalphotomask exposure and the semi-transparent imprint mask. The typicalphotomask includes a glass plate having on one side a metal (typicallychrome) layer from which metal has been selectively removed to form apattern of optically transmissive and opaque areas. This photomask plateis placed in contact with a photosensitive layer on a substrate and thephotosensitive layer is exposed by light passing through the transparentareas of the photomask plate. Because the photomask pattern layers areessentially planar, light that is transmitted through the openings candiffract, scatter and spread and make multiple bounces within the resistlayer, thereby causing the unwanted exposure of areas that should nothave been exposed. Diffraction is particularly problematic for finerfeatures (below a few microns), limiting the use of photomasks withstandard (visible) light sources to larger (multi-micron) features andabove. In order to form patterns with smaller features, shorterwavelength light sources and more precise mask handling are required,and this can become prohibitively expensive for nanoscale features. Thusthe NIL process, being essentially mechanical imprinting, can overcomethese problems, except for the addition of the problem of imprintresidue removal. Thus the S-T mask tools made by the subject technologycan both readily form submicron features while eliminating the plasmaresidue removal step.

FIG. 1 illustrates an example of an improved method of the presentdisclosure for forming a semi-transparent imprinting tool. FIG. 1depicts a substrate 100 which includes a support layer 104 (which can betransparent or flexible) having a “seed” layer 103 over which is formeda patterned relief layer 101. The seed layer 103 can be a layer of anyone or more suitable materials that can enable electro- or electrolessplating of a material from solution, particularly a metal or metalalloy. For electroplating, this seed layer 103 can include or be formedof an electrically conductive metal, such as Ni, Ag, Au, etc., but canalso be a conductive polymer (PEDOT:PSS), an transparent conductiveoxide (‘TCO’) such as indium tin oxide (ITO), conductive carbon, etc.For electroless plating, the seed layer 103 can include or consist ofvery small nanoparticles that nucleate chemical deposition. Both typesof plating are well known and have been used for many years. The seedlayer can include or be formed of an electroless metal nucleation layerfor the electroless deposition of metals, such as but not limited to,Ni, Cu, Ag, Au, etc. The relief pattern can be applied over the seedlayer 103; in some embodiments, the relief pattern can be electricallynon-conductive, e.g., for electroplating, or can form a nucleation site,e.g., for electroless deposition. Relief pattern 101 can be formed on orin a layer of material that can be composed of or include a suitablepolymeric material such as a radiation-curable acrylic polymer or otherradiation-curable material. For some embodiments, relief pattern 101 canbe formed by the radiation activated crosslinking of a suitable monomersolution. In an exemplary embodiment, relief pattern 101 can be formedin a material layer including a radiation-curable acrylic polymer madecommercially available as Norland Optical Adhesive NOA 72 (NorlandProducts Inc., Cranbury N.J.). As shown, relief pattern 101 has openings102 that expose the underlying seed layer for subsequent plating. Forthe purposes of this discussion, relief pattern 101 may be referred toas a “relief mask” or “polymer mask” or (in the case reserved for theformation of an original pattern), a “master pattern”. This distinction,however, is not of major significance, as subsequent processing isgenerally similar.

FIG. 2 shows substrate 100 after metal 105 has been deposited inopenings 102 (FIG. 1) from the action of a plating bath (not shown). Thethickness of the metal layer is proportional to the electrical chargetransferred during the electroplating, and the time, temperature,concentration etc., for electroless plating. The plating can beterminated when the desired metal thickness (height) is reached. FIG. 3shows an example in which metal 105 is plated until it reaches the topof relief pattern 101. For the purposes of this discussion, thestructures shown in FIGS. 2 and 3 will be referred to a “donor layer” or“donor sheet”, the reason for which will become obvious subsequently inthis discussion.

FIG. 4 depicts structure 110 in which a transparent adhesive layer 106is bonded to a transparent upper substrate 107. Bonding can be carriedout by lamination (by roll or press, etc.) of the plated lower substrateshown in FIG. 2 or 3 to a transparent upper substrate using atransparent adhesive as the lamination agent. UV curable, epoxy,silicone, pressure sensitive, etc. can be used for this bonding step,but the adhesive preferably has adequate adhesion to the plated metal sothat the metal does not separate during subsequent imprinting use. FIG.5 shows structure 120 in which the filled relief pattern is bonded tothe upper substrate.

FIG. 6 a depicts the delamination of the lower substrate (“donor sheet”)from upper structure 130, where separation has occurred at the interfacebetween the seed layer 103 and the support layer 104. For the purposesof this discussion, structure 130 and the like will be referred to as“receiving layers” or “receiving sheets”.

For certain applications, such as, for example, OLED lighting andcertain PV cells, it is can be beneficial to leave pattern layer 101and/or seed layer 103 in place, as this will produce an essentiallyplanar surface, where using a transparent seed layer 103 (such as ITO,carbon nanotubes, silver or other metallic nanowires, organic conductorPEDOT:PSS, etc. or other transparent conductive materials) can providecontinuous electrical conductivity (“field conductor”) over the entiresurface rather than just the metal pattern, for applications where thisis beneficial or required.

FIG. 6 b depicts the separation of donor sheet 104 from receiver sheet140, but in this example the delamination occurs at the interfacebetween the seed layer 103 and the plated relief mask layer. Althoughthis illustration shows fully filled relief structure, a partiallyfilled structure, such as shown in FIG. 2, can also be used.

FIG. 6 c shows a third embodiment of the delamination step, where inthis example receiving sheet 150 separates from the lower substrate atthe interface between the relief mask 101 and the plated metal/adhesivelayers 105/107 without destruction of the relief structure. Oneadvantage of this embodiment is that, by selecting a seed layer with lowadhesion to the plated material (such as ITO and Ni, respectively, forexample) and the use of an imprint polymer (such as a radiation-curedacrylic polymer, etc.) that likewise has low adhesion to the platedmetal and bonding material, the subsequent separation leaves the moldintact for re-use. The 3 cases illustrated in FIGS. 6 a-c each haveadvantages, and the application of specific release layers at theinterface where separation is desired (not shown) can be used tofacilitate the desired separation.

The step that is carried out after separation depends upon which of the3 separation methods were used to produce the receiving sheet. In thecase shown in FIGS. 6 a and 6 b, the inclusion of a release layer at theselected interface can facilitate the desired separation, although it isalso possible to selectively use materials for this process whoseintrinsic adhesion allows natural separation at the desired interface.For example, if the seed layer has weaker adhesion to the lowersubstrate than it has to the plated metal/relief pattern material, thenseparation will occur at the lower substrate. Depending upon whichlayers that remain with the receiving sheet, chemical or plasma etchingare used to selectively remove the seed layer (not shown) and/or part orall of the relief pattern.

This is illustrated in FIG. 7 a-c, where FIG. 7 a shows the case ofseparation at the seed layer-plated metal interface (FIG. 6 b) toproduce structure 140. FIG. 7 b shows partial removal of the reliefpattern material to produce structure 142, and FIG. 7 c show completeremoval of the relief pattern material to produce structure 144.

The methods of this invention allow the opportunity to modify both themetal thickness (for optimum opacity or electrical conductivity) and thestep height of the relief pattern. The depth (or ‘height’) of the reliefpattern can be adjusted by the degree of etching used to remove the seedand mask material (FIG. 7 d). Thus tools can be formed whose relief isgreater (117) or lesser (108 in FIG. 7 d) relief than the original bythe means of this invention, which represents a considerable savings intime and cost compared to generating another master pattern.Furthermore, plasma etching of the seed/polymer layer in a S-T tool ismore selective than carrying out the same process with a thin-film metalmask, as described in the prior art. This is because the plated metalwill have a negligible plasma etch rate compared to that of the polymerrelief pattern using the typical plasma gas mixture used for polymers,allowing deep etching in which the etched area is confined to thepolymer area, minimizing the undercutting that would otherwise occur ifthe metal was a thin-film layer.

The case in which a release layer is applied to the S-T tool is shown inFIG. 7 e, where layer 113 is a Teflon-based or other such low-adhesionlayer, as is known to the art is used to facilitate separation, whenneeded.

An example of the use of the improved semi-transparent imprinting toolis given in FIG. 8 a-d. In FIG. 8 a, structure 150 can include asubstrate in contact with the tool and an intervening imprinting fluid.A lower substrate 118 (rigid or flexible, transparent or opaque) iscoated with the metal layer 111 to be patterned. A semi-transparent toolincluding support 106, adhesive layer 107, and opaque pattern 105 isplaced into contact with the lower substrate wherein a layer ofradiation-curable monomeric material 115 is spread between the tool andthe substrate. A radiation source 112, which is capable of causingsolidification (e.g., by cross-linking) of material 115, is applied fromthe back side of the semi-transparent tool, whereby only the transparentparts of fluid 115 are irradiated and hardened. Structure 160 of FIG. 8b shows the hardened material 115′ and the un-hardened material 116under the opaque tool elements 105. The depth of the opaque elements ofthe tool traps the radiation and minimizes stray reflections fromexposing the material 116 under the opaque elements. After exposure hasbeen completed, the tool and substrate are separated, forming structure170 shown in FIG. 8 c. Un-hardened residue 116 can be readily removed bydeveloper, solvent or other chemical means. FIG. 8 d illustrates thesubsequent processing of the masked substrate after residue removal,where chemical (or plasma) etching known to the art is used to removemetal from the area 118 exposed through the polymeric mask. The resultis layer 111′ having metal layer selectively patterned. The last step(not shown) is the removal of the spent polymeric mask 115′, which canbe done using chemical means (e.g., a solvent, developer, etc.) ormechanical means. It should be noted that, in exemplary embodiments,this critical step reveals the patterned metal layer, which ispreferably free of debris and un-removed mask material. This is asignificant problem when such masks are plasma etched to remove theresidue layer, as plasma hardening makes these materials virtuallytotally resistant to chemical removal, and mechanical means can often beproblematic and result in incomplete polymer removal.

Experimental details of one embodiment of the formation of asemi-transparent imprinting tool are as follows: a commercial filmconsisting of a 7 mil thick polyethylene terephthalatephthlate (PET)support and an electrically conductive ITO layer having a surfaceconductivity of 100 ohms/square (SP-7013-100-5 from Techni-Met Inc.,Windsor Conn.) was used as the lower substrate plus seed layer and arelief pattern was formed on the ITO surface using the well-knownprocess of a transparent imprint tool and an acrylic UV adhesive. Thepattern consisted of 20 micron wide trenches that were 4-5 microns deep,and the residue layer at the bottom of the trenches was removed byplasma etching using a inductively coupled plasma (ICP) equipped TrionMinilock II (Trion Technology, Clearwater Fla.) with an O2/Ar gasmixture, a process known to the art.

The substrate with cleaned relief pattern was immersed in a Ni sulfamateelectroforming bath having a Ni foil anode, and electrical contact wasmade to an expose section of the ITO layer of the patterned substrate toform the cathode. A current of 0.5 A at 5 V was used to deposit a 3-4micron thick layer of Ni in the trenches at which time the substrateswas removed from the electroforming bath, rinsed and dried. Thesemi-transparent tool so formed was used to imprint another acrylicmaterial using long-wave UV radiation to cross-link the monomer on a 5mil thick PET substrate that had been coated with a 100 nm thick layerof aluminum, where the exposure radiation was from the semi-transparenttool side during curing (typically less than 5 sec cure time). The tooland substrate were separated and the uncured monomer (“residue”) wasremoved by isopropyl alcohol rinse. The thus-formed polymer maskedsubstrate had no residue layer and did not require plasma etching andcould thus be further etched to remove the exposed aluminum metal bychemical etching.

The method of the subject technology for producing S-T tools can also beused to form transparent conductive structures, such as a TCF. In thiscase, the plated metal (such as Ag, Au, Ni, Cu etc.) is selected for thedesired conductor properties rather than solely for its imprintingdurability (such as electroformed Ni), and the plating conditions(current/voltage, time, temperature etc.) are used to control thethickness of the deposited metal, which in turn will produce the desiredelectrical conductivity of the TCF. Because plating processes arecapable of depositing many microns of metal in a matter of minutes, itis possible to achieve high surface conductivities (to less than 1ohm/square) by forming thicker conductive grids with this method. Thisis significant for transparent conductors that are used in high currentapplications, such as large-area OLED lighting and PV energy conversion.The roll formation of such films, as well as S-T tool films, isillustrated in the following example.

FIG. 9 shows a roll-to-roll process that can be used either to formsemi-transparent imprinting tools (S-T tools) or to form suchtransparent conductive films (TGFs), as described above. Apparatus 400can include a continuously rotating plating cylinder (or belt orspool-to-spool configuration) 430 immersed in plating bath 422, which inthe case of this example is an electroplating bath, although anelectroless plating bath can also be used according to the disclosedelements of this invention. The plating drum 430 can include a permanentseed layer 403, such as a metal or conductive oxide or polymer or othermaterial whose adhesion to the material deposited by the bath isrelatively weak, and a polymeric layer 401 is used to form the reliefpattern. In this example, the conductive layer 403 is ITO (andpassivated Ni has also been used), and deposited metal 405 was Nideposited from a Ni sulfamate electroforming bath 422, a process wellknown to the art. A rotary slip-ring (not shown) is used to make contactwith the cathode (the conductive layer 403), and Ni anode 426 is used toreplenish the Ni deposited from the plating solution. The circuit isestablished by connecting the anode and cathode to power supply 248. Asdrum 430 rotates, metal 405 is deposited on conductive layer 403 throughpattern openings 402. The thickness is controlled by platingvoltage/current, temperature and bath dwell time, and the plated metalis transferred from the drum to the receiving substrate 406 from asupply roll (not shown) by action of adhesive 407 (which can beradiation-activated, heat-activated, epoxy, pressure sensitive or othertransparent adhesive). Rinsing of the plated drum may be optionallycarried out, as needed, prior to lamination to substrate 406. Thesubstrate 406 with metal layer 405′ removed from the drum issubsequently rewound onto take-up spool 421, while the drum area 402from which the metal has been removed is re-immersed in the plating bathfor deposition of more metal.

In addition to the roll-to-roll plating process to form S-T tools andTCFs, flexible S-T tools can also be incorporated into a roll-to-rollimprinting process to produce polymer relief masks in large quantities.Such masks are used to form fine-detailed conductive structures used inflexible electronics, touch screens, displays, OLED lighting, PV cells,as described previously. FIG. 10 depicts the embodiment of the use of arotary S-T tool in a continuous roll-to-roll imprinting process forproducing a film having a polymer relief mask that can be used forsubtractive or additive processing, but without requiring the film beplasma etched. In this example, an imprint drum assembly 530 can becomposed of or include a transparent support drum (drum or belt) elementto which is adhesively bonded a length of S-T tool made any of by themethods disclosed above. Transparent support 506 of the S-T tool isbonded with a transparent adhesive (radiation curable, thermal adhesive,pressure sensitive, epoxy, etc.) to the transparent support 536 (notshown in detail to eliminate clutter in sketch). The example in FIG. 10illustrates a subtractive process in which a metallized plastic film 531is to be patterned. A UV-cure monomer 516 is applied to the surface ofdrum 530 (although it can be also applied to film 531), which islaminated against drum 530 and film 531 with the action of pressureroller 532. Here, an exposure configuration in required in which theradiation source (for example, from solid-state diodes whose outputwavelength is capable of causing the imprint fluid to cross-link) ismounted inside the rotating semi-transparent imprint drum. As the drumrotates in contact with the film, radiation from the light source 538 istransmitted through the rotary S-T tool to harden fluid 516. An exposureshield 534 is provided to prevent premature exposure of the imprintfluid. The film is continuously delaminated from the S-T drum at roller533, with the film at this point including hardened relief pattern 515′and un-cured residue layer 516 on metal layer 511. The next steps (notshown) include removal of un-cured residue layer 516 by transportthrough a chemical rinse tank, the either rewind or metal removal bytransport through a chemical etch tank.

Accordingly, aspects and embodiments of the subject technology inaccordance with the description herein can afford one or more advantagesrelative to prior techniques and art. For example, aspects andembodiments of the present disclosure can provide for the elimination ofa plasma etching step. The plasma etch process generates a large amountof very short wave radiation and ion bombardment, as well as possiblere-deposition of etch by-products. This can have a strong effect on thepolymeric mask material, particularly in extreme crosslinking andsurface reactions that make subsequent mask removal very difficult, ifnot impossible. By eliminating the plasma etch step, the polymer maskcan be readily removed from the metal layer using relatively mildchemical treatment and minimization of damage to the underlying metallayer.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows and to encompass all structural andfunctional equivalents. The foregoing notwithstanding, none of theclaims are intended to embrace subject matter that fails to satisfy therequirement of Sections 101, 102, or 103 of the Patent Act, nor shouldthey be interpreted in such a way. Any unintended embracement of suchsubject matter is hereby disclaimed.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

What is claimed is:
 1. A semi-transparent imprinting templatecomprising: a first layer an optically transparent support surface; atransparent bonding second layer in contact with the first layer; and athird layer in contact with the second layer, the third layer includinga physical relief pattern wherein the relief pattern includes spatiallyselective areas of optically opaque material and spatially selectiveareas of optically transmissive material, wherein the spatiallyselective areas of optically opaque material include a plated metal,wherein the spatially selective areas of optically transmissive materialinclude a polymeric material.
 2. The semi-transparent imprintingtemplate according to claim 1, wherein the optically opaque material isdeposited by the method of electro- or electroless plating.
 3. Thesemi-transparent imprinting template according to claim 1, wherein thedimensions of the opaque material in the direction generallyperpendicular to the first surface is controlled by the amount of platedmaterial.
 4. The semi-transparent imprinting template according to claim1, wherein the dimensions of the opaque material in the directiongenerally perpendicular to the first surface is controlled by theremoval of a selected amount of transparent material.
 5. Thesemi-transparent imprinting template according to claim 1, wherein thedimensions of the relief features are in the range from about 0.01 μm toabout 200 μm.